Problem in Fluid Valve.

Hi, first of all i would like to thank anyone who can help me in my problem in advance.😀

My Problem is that I want to make a prototype that will automatically "refill" the water in the tank. When the tank is completely empty.

Please refer to my diagram so that you will not be confused.

Here are the scenario.

The Fluid Valve A will not open unless the Fluid Valve B is closed. And the water inside the Fluid Tank is completely empty. And will close when the Water Level Sensor is triggered.

The Fluid Valve B is operated by a push button switch. That has a 20 seconds duration before it closes. And it should not work if the Fluid Valve A is open.

What are the types of material will a use? (Valves, Timers, Switches, PCB circuit)

my email address is
I'm a senior Electronics and Communication Engineering Student.
Thanks a lot in advance.